The standard turbidity produced by one mg of silicon dioxide (silica) in one litre of distilled water, is called
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One True Colour Unit (TCU) is the colour produced by
The threshold odour number (TON) for a water sample of 40 ml, diluted to standard 200 ml mixture, in which odour is just barely detectable to the sense of smell, is
Threshold odour number represents the dilution ratio at which the odour is hardly detectable,
TON = 200/40 = 5
Water is considered ‘hard’, if its hardness is of the order of
Water with hardness upto 75 ppm are considered soft while those with 200 ppm and above are considered hard. In between the waters are considered as moderately hard.
Higher quantities of copper, more than 2.5 mg/l or so, may cause diseases pertaining to
High quantities of copper are likely to affect human lungs and other respiratory organs.
The maximum allowable concentration of iron in water is
Higher concentration of iron above 0.3 ppm causes discolouration of clothes and incrustation in water mains.
The commonly used indicator for measuring iron concentration in water is
Eriochrome black T is used to measure hardness. Phenolphthalein is used to measure alkalinity. Blue litmus is used to measure acidity of water.
The maximum safe permissible limit of chlorides in domestic water supplies is
Breweries and distilleries preferably require